Kernel Log: Apple streamlines CUPS
by Thorsten Leemhuis
CUPS 1.6, which is currently in development, will no longer include some features used in many Linux distributions. An Intel developer has presented patches that may allow the kernel to use an efficient power management feature by default.
On his blog, Tim Waugh, the developer of the system-config-printer printer configuration program used in distributions such as Fedora and Ubuntu, has pointed out that changes in CUPS 1.6, which is currently in development, will affect the Linux world. According to Waugh and openprinting.org maintainer Till Kamppeter, version 1.6 of the open source printing system developed by Apple since 2007 will no longer include several features that are "not much interesting" to Mac OS X but are used in many Linux distributions.
Among them is the "CUPS Browsing" support – until now, CUPS servers have used network port 631 to broadcast all available printer queues that allow client systems to discover printers automatically. In Mac OS X, CUPS has long used DNS-SD (DNS-based Service Discovery) to perform this task. However, CUPS doesn't yet co-operate with Avahi, a system many Linux distributions use for zeroconf technologies such as DNS-SD. Waugh has already integrated patches to change this in Fedora, and he has also submitted these patches to the CUPS project for inclusion. On his blog, the developer explains that, in future, automatic CUPS queue discovery will require Avahi to be running on both the server and the clients; he adds that operation without Avahi is possible, but it won't allow CUPS to detect printer queues automatically.
Waugh and Kamppeter say that, with version 1.6, the CUPS project will also drop various filters that are irrelevant to Mac OS X. The OpenPrinting project has already picked up these filters and plans to maintain them as part of the newly created package cups-filters. That also includes PDF-handling filters that were never part of CUPS.
Waugh had previously informed the Fedora developers of these changes. During the resulting discussions, Waugh indicated that several developers had considered a fork of CUPS as well as alternative solutions. Waugh said that these are not ruled out for the future, but that they aren't considered beneficial at present.
Next round: Intel's RC6
Intel developer Eugeni Dodonov recently submitted two patches for discussion that allow the kernel to enable the RC6 power management technology by default in Intel's Sandy Bridge processors with Graphics cores. However, the technology will also make the kernel avoid the deepest sleep states because it cause problems on some systems; in kernels that include this modification, the use of these "deep rc6" and "deepest rc6" modes can be enabled using a parameter. The developers are still discussing whether to submit the patches for inclusion in Linux 3.3; the power management feature is particularly relevant for notebooks and can reduce power consumption by 5 Watts on some systems, which causes fans to kick in less frequently and at a slower speed and considerably prolongs a computer's battery life.
In two blog postings, Dodonov had previously discussed some of the most recent developments regarding the graphics drivers for Intel desktop and notebook chips (1, 2). In the second posting, he mentions a patch that the developers hope will enable them to find the causes of the problems with RC6.